In a wind turbine, a hydraulic pitch system is used to control the pitch angle of the rotor blades in order to optimise the wind energy production and to ensure that the rotor blades are not subjected to too large loads when strong winds are blowing.
Since pitching actions require activity from the pitch cylinders, a potential hazard exists in situations where persons are located inside the hub, for instance during blade installation or pitch system maintenance.
If the blades are not fully extended and the normal control system is activated, personnel may potentially be injured or, in severe circumstances, crushed between the moving pitch cylinders and the stationary hub wall.
Thus, there is a need for providing a system which protects the service technician and others in the hub of the wind turbine from unintended and dangerous situations.